Impact mill



' Feb. 23, 1932. L. KOLLBOHM 7 1,847,009

IMPACT MILL Filed Feb. 18, 1929 2 sheets-sheet 1 Fig.1.

Feb. 23, 1932. KOLLBOHM 1,847,009

IMPACT MILL Filed Feb. 18 1929 2 Sheets-Sheet 2 Inventor:

Patented Feb. 23, 1932 UNITEosTATES Puma-,1 OFFICE LUDW'IG- KOLLBOHM, OF HAGEN, GERMANY, ASSIGNOR OF ONE-HALF '10 DEUTSCHE ZB ABGOOK- UNI) WILCOX-DAMPFKESSEL-WEBKE A. 6., OF OBEREAUSEN/BHINELAND,

mac! MILL Application fled February-18,1952.9 Serial No. 340,887, and in Germany February 23, 1928.

In the known so-called impact mills, the material to be disintegrated is thrown against an impact surface b a current of compressed air, and thereby (material to be disinte rated must be flung against the impact sur ace with considerable force it is necessary to introduce the current of air that moves'the said material at a considerable pressure, so that the entlre vessel in which the grinding operation proceeds is subjected to pressure. Now it has been found that the disintegrating action is checked to a remarkable extent in a space subjected to 0 is obviated by evacuating the interior by means of a suction blower and maintaining a vacuum therein preferably amounting to from 50 to 80'millimetres of water. The energy of the current of compressed air that 'moves the material to be ground then produces its full effect, without the interior of the grinding apparatus being'exposed toa pressure thatwould obstruct the disintegra tion of the material.

According to the invention the effectiveness of this disintegrating apparatusiis substantiall enhanced by a special construction of the ollow body that guides the current of air carrying the material to the impact surface facing the said hollow body, and ofthe grinding casing. The hollow body, which guides 1n its interior the mixture of compressed air and material to be ground, at a high velocity, forms at the same time, by appropriate construction of its outer walls, the

' internal closure of the circular conically and spirally tapering suction space for the mater1al, while a suitably shaped grinding cas ing forms the external closure. The impact surface has a concave curvature like that of a hollow cone, a paraboloid or the like, whereby the result is obtain d that the material leaving the conicall flaring 'hollow body strikes perpendicularly against the impact surface and is thrown back, whereby the wear isintegrated. Since theof the impact surface is effectually diminished. Furthermore by the mutual impact of the particles of material approaching and leaving the impact surface the disintegration is assisted.

By a central arrangement of the inlet for of the mill throughout its periphery is obtained, and an intimate mixing of the fresh material with the material that is already in circulation and partially disintegrated, whereby a preliminary disintegration is already initiated. The grinding casing contains screened apertures for a sup ly of secondary air, which roduces a rea ily transportable mixture o ground material and air. In the lower portion, tangentially entering scavenging air pipes serve effectually to obviate stoppages.

Various constructional forms of the invention are illustrated by way of example in the accompanying drawings, in which Figure. 1 shows in sectional elevation an impact mill according to the invention,

Figure 2 shows on a smaller scale a second constructional form in section,

V Figure 3 illustrates theexplanation of the method of working of. the impact mill,

Figure 4 is a v1ew similar to Figure 2 of an impact mill according to Figure 2 with an increased output.

Figure 5 is-a section on the line 5-5 in Fig. 4, and Figure 6 shows a further constructional form of the impact mill according to the invention.

In the impact mill according to the invention'illustrated in Figure 1, the material to be ground is supplied through an inlet pi e In with a double sluice e to the casing a o the mill, and slides down the downwardly'tapering hopper-like wall of the casing to the lowest point of the mill, where compressed air is introduced through a nozzle d. At a suitable height above this nozzle is located a guiding and scattering body I), by which l but e height thereof is adjustable. Prefera'bl above the impact plate there is com nected to the casing a a suction blower g, by

which a-partial vacuum is sustained in the the funnel-shaped walls of the casing a and are again thrown against the impact plate by the current of compressed air. a

By employingJ hot air. for'drivin the material, it is oss1 le during the grin ing process to dry t e material at the same time.

In the constructional form of the invention accordin to Figure 2, there is likewise rovided in t e casing a an n wardly flaring guidin and scattering b0 y b serving to supply t e material to be ground. Above this guiding and scattering body 1; is arranged the impact body 0, which has a concave curvature facing the mouth iece of the scattering body b. The material entering at k is here distributed conically over the impact body 0' and passes into the suction space m. By the screened secondary air supply ducts i, the material to be ground is thorou hly mixed with air. The mixture of material and air passes into the nozzle-like lower portion oft e guiding and scattering body 6', and is brought to a high velocity in the cavity 11. by the compressed air supply d and is thrown in jet form against the hemispherical impact surface 0', in such a manner that the individual particles meet the impact'surface perpendicularly. Under these circumstances a disintegration will occur the more energetically, as the particles of material approaching and leaving the impact plate are whirled together and disintegrate one another by mutual friction.

The particles of material retain the hi h. velocity imparted to them until they stri e the impact plate while the compressed air in the guiding body b in conse uence of its diffuser-like form, gradually o'ses its velocity, so that the separation of the sufficiently disinte ated material is thereby facilitated. By t e exhauster connected to the mill casing a at e there is produced in the mill a rarefaction of air, WhlCh effects first a sifting of the enterin material and then a sifting of the materia thrown oflz' b the impact surface, while all the still insu ciently disintegrated particles of the ground material ass into the space m, where the pressure is low atmospheric, and are reintroduced into the circuit.

The compressed air nozzle d the guiding and'scattermg body I), and the impact body a are according to the invention adjustably arranged in the casing a, so that they can beadjusted accordin to the nature of the ma terial to be treate Figure 3 enables the method of operation of the jet-like splitting of the material conve ed to be better understood.

igures 4 and 5 show in sectional elevation and plan respectively the construction of the ucts n acting in the manner ereinbefore described are present, towhich there correspend a common impact surface or a plurality of associated impact surfaces, whereby the output' admits of being considerably, increased in a casing WhlCh is 'onl 'slightl larger. Each of the compressed air pipes 11: pertaining to the individual guiding and scatteringbodies is capable of being sepaof guiding rately shut off, thereby enabling the output j to be regulated within wide limits. In order to obviate stoppages at the bottom of the casing a,, compressed air can be introduced from time to time through tangentially openlng compressed air pipes k provided witli shut-ofi members, for the purpose of eliminating if necessary deposits of material. Secondary air is supplied through the screened ducts 5 ,5 o v Figure 6 shows a modified constructional form of the invention, wherein instead of compressed air, air delivered under pressure by a hi h is employe n this case the pressure connection of the blower f is introduced into the bottom of the grinding casing a so that this pressure connection wholly or (as illustrat-.

ed) part1 replaces the guiding and scattering bo y 6 at the same time. Between the pressure connection 7 and the guiding body 6 a rarefaction of air is produced in the circular' slot g introduced in the direction of pressure, and the material is thereby drawn out by suction and carried away according to Figs. 1 and 2. The disintegrating process is the statue as in the mills according to Figs. 1 to 3 previously described.

What I claim is 1. An impact mill for disintegrating solid material, comprising a casing, an 1m act plate in the casing, a nozzle ada ted to a it a jet of compressed air into t e casing to throw material thathas been introduced into the casing against the said impact plate, a suction blower adapted to maintain a pressure below atmospheric pressure in the easing, and screened inlets for admitting secondary air to the casing to mix with the material that is being disinte ated.

2. An impact mill for dlsintegrating solid .material, comprising a casing, an impact plate in the casing, a nozzle adapted to admit a jet of compressed air into the casing to throw material that has been introduced into the casing against the said impact plate, a section blower adapted to maintain a pressure below atmospheric pressure in the casing, and means for admitting scavenging air into the bottom of the casing under pressure.

3. An impact mill for disintegrating solid material, comprising a casing, an impact plate in the casing, a nozzle adapted to admit a jet of compressed air into the casing to throw material that has been introduced into the casing against the said impact plate, a suction blower adapted to maintain a pressure below atmosheric pressure in the casing, and means for admitting scavenging air into the bottom of the casing tangentially under pressure. I

4. A11 impact mill for disintegrating solid material, comprising a closed casing having an inlet for admitting material to be disintegrated thereto, a nozzle arranged to admit a jet of compressed air into said casing, an impact plate arranged in the casing in a position to be impinged by the jet of air issuin from the nozzle and the material carried along with the air, the portion of theinter: ior of the casing in the vicinity of the impact plate constituting a disintegrating zone, and suction means in communication with the disintegrating zone for removing the disintegrated material and maintaining the interior of the casing at sub-atmospheric pressure, the inlet for the material, the'impact plate and the disintegrating zone being located in the upper part of the casing.

In testimony whereof I have signed my name to this specification.

LUDWIG KOLLBOHM. 

